Add build log file storage and download functionality

- Write deployment logs to files when deployment finishes (success or failure)
- Log files stored in DataDir/logs/<hostname>/<appname>/<appname>_<sha>_<timestamp>.log.txt
- Capture commit SHA for manual deploys by parsing git rev-parse HEAD after clone
- Add download endpoint for log files at /apps/{id}/deployments/{deploymentID}/download
- Add download link in deployment history view for finished deployments

internal/handlers/app.go

@@ -5,6 +5,8 @@ import (
 	"database/sql"
 	"encoding/json"
 	"net/http"
+	"os"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"time"
@@ -438,6 +440,66 @@ func (h *Handlers) HandleDeploymentLogsAPI() http.HandlerFunc {
 	}
 }
 
+// HandleDeploymentLogDownload serves the log file for download.
+func (h *Handlers) HandleDeploymentLogDownload() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		appID := chi.URLParam(request, "id")
+		deploymentIDStr := chi.URLParam(request, "deploymentID")
+
+		application, findErr := models.FindApp(request.Context(), h.db, appID)
+		if findErr != nil || application == nil {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		deploymentID, parseErr := strconv.ParseInt(deploymentIDStr, 10, 64)
+		if parseErr != nil {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		deployment, deployErr := models.FindDeployment(request.Context(), h.db, deploymentID)
+		if deployErr != nil || deployment == nil || deployment.AppID != appID {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		// Get the log file path from deploy service
+		logPath := h.deploy.GetLogFilePath(application, deployment)
+		if logPath == "" {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		// Check if file exists
+		_, err := os.Stat(logPath)
+		if os.IsNotExist(err) {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		if err != nil {
+			h.log.Error("failed to stat log file", "error", err, "path", logPath)
+			http.Error(writer, "Internal Server Error", http.StatusInternalServerError)
+
+			return
+		}
+
+		// Extract filename for Content-Disposition header
+		filename := filepath.Base(logPath)
+
+		writer.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		writer.Header().Set("Content-Disposition", "attachment; filename=\""+filename+"\"")
+
+		http.ServeFile(writer, request, logPath)
+	}
+}
+
 // containerLogsAPITail is the default number of log lines for the container logs API.
 const containerLogsAPITail = "100"